#!/usr/bin/env node

const {Readable} = require('stream');//这个不可以改名，因为这属于对象的解构
//==
//const Readable = require('stream').Readable;这个可以改名

const rs = new Readable();
let c = 'a'.charCodeAt(0);
rs._read = () => {
  //方法一
  for(c;c < 'z'.charCodeAt(0);c ++){
    rs.push(String.fromCharCode(c));
  }
  //方法二
  /*rs.push(String.fromCharCode(c++));*/
  //if(c === 'Z'.charCodeAt(0) + 1)
    /*rs.push(null);*/
}

rs.pipe(process.stdout);
